Self Consumption Sizing Calculator

1. Enter your average daily energy use and your daytime share.
2. Add peak sun hours and estimated system losses for your area.
3. Choose a self‑sufficiency target that fits your goals.
4. Set evening coverage and autonomy to size storage conservatively.
5. Enter tariffs and costs to estimate savings and payback.
6. Press Calculate to view results above the form.

Load profiling and daytime share

Self‑consumption improves when solar output overlaps with household demand. Start with average daily kWh and estimate what fraction runs during daylight, such as cooling, pumps, or home‑office loads. A higher daytime share increases direct use and reduces exports, often lowering the battery size needed for the same coverage target.

Many households also benefit from modest load shifting. Running laundry, dishwashing, or water heating during peak production can lift direct self-use without new hardware. If you plan electric vehicle charging, estimate daytime charging hours carefully. Flexible loads effectively act like storage and can reduce required battery capacity in many practical designs.

Sizing solar for self‑sufficiency

This calculator converts peak sun hours into annual energy per installed kW, then scales the array to meet a chosen self‑sufficiency target. Losses capture inverter, wiring, shading, and temperature impacts, so using realistic values matters. If you set a very aggressive target with low sun hours, the recommended array grows quickly and exports may rise.

Battery capacity and autonomy tradeoffs

Storage is sized from evening demand, desired coverage, and autonomy days. The model accounts for round‑trip efficiency and depth-of-discharge limits, translating usable output into a larger nominal capacity. Increasing autonomy from one to two days roughly doubles storage needs, while improving efficiency or allowing deeper discharge reduces the required kWh.

Tariffs, exports, and cashflow

Financial outputs compare a baseline grid bill to a post‑solar estimate using daily grid import and export. When export credits are low, prioritizing self‑use can produce stronger savings than simply adding more panels. Enter local rates, installed costs, and annual O&M to compute net benefit and a simple payback indicator.

Using results to refine design

Use the energy balance chart to check whether the system is export‑heavy or import‑heavy on a typical day. If exports dominate, consider shifting loads to midday, adding smart scheduling, or increasing storage coverage. If grid imports remain high, raise the self‑sufficiency target or verify daytime share and loss assumptions with better data.

1) What does self‑consumption mean?

It is the portion of solar generation used on‑site, either directly or after being stored in a battery. Higher self‑consumption usually reduces exports and increases the value of each kWh produced.

2) Why do losses matter so much?

Losses reduce usable solar output. Temperature, inverter efficiency, wiring, and shading can meaningfully lower production versus nameplate ratings, so using a realistic loss percentage prevents under‑sizing.

3) How is battery size estimated here?

The calculator sizes storage from evening energy you want covered, multiplied by autonomy days, then adjusts for round‑trip efficiency and depth‑of‑discharge. It produces a planning‑level nominal kWh value.

4) Can this model handle time‑of‑use pricing?

Not directly. It uses an average import rate and a single export credit. If your pricing varies by hour, run separate scenarios using blended rates that reflect your expected charging and usage behavior.

5) Why might a larger solar system increase payback time?

When export credits are low, extra production may be sold cheaply. If the additional kWh are not consumed on‑site, the added cost can outweigh added savings, extending simple payback.

6) What inputs improve accuracy the most?

Better daytime share estimates, local peak sun hours, and an accurate loss percentage typically have the biggest impact. If available, use smart‑meter data or bills to validate daily kWh and seasonal patterns.